Лікар оглянув щелепу.

Because it is the direct object of the verb оглянув.

The dictionary form is щелепа. In this sentence, the doctor examined the jaw, so jaw is the thing receiving the action. In Ukrainian, a feminine noun ending in -а usually changes to -у in the accusative singular:

• щелепа = nominative singular
• щелепу = accusative singular

So:

• Лікар = the doctor
• оглянув = examined
• щелепу = the jaw

Оглянув is the past tense, masculine singular form of the verb оглянути.

It tells you that:

• the action happened in the past
• the subject is singular
• the subject is grammatically masculine

Related forms would be:

• оглянув = he examined
• оглянула = she examined
• оглянуло = it examined
• оглянули = they examined

So this sentence specifically sounds like the doctor is male, unless context overrides that in some unusual way.

This is a question of aspect, which is very important in Ukrainian.

• оглянути / оглянув = perfective: a completed act of examining
• оглядати / оглядав = imperfective: examining, used to examine, was examining, or repeated/ongoing examination

So Лікар оглянув щелепу presents the examination as one completed event.

If you said Лікар оглядав щелепу, it would sound more like:

• the doctor was examining the jaw
• the doctor used to examine the jaw
• the focus is on the process, not completion

Mainly from the case endings.

• лікар is in the nominative, which is the usual case for the subject
• щелепу is in the accusative, which is the usual case for a direct object

So even if the word order changed, the endings would still help tell you who did what.

Also, the verb оглянув agrees with the subject in gender/number, and it matches лікар as a singular masculine subject.

Yes, лікар can be used as the professional title doctor in a general sense, including for a woman in some contexts. But in this exact sentence, the verb оглянув is masculine, so the sentence points to a male doctor.

If you wanted to make the doctor clearly female, you could say:

• Лікар оглянула щелепу.
• Лікарка оглянула щелепу.

The first keeps лікар but changes the verb to feminine. The second uses лікарка, an explicitly feminine noun.

No. Ukrainian word order is fairly flexible because case endings carry a lot of the grammatical information.

The most neutral order here is:

• Лікар оглянув щелепу.

But you could also hear:

• Щелепу оглянув лікар.
• Оглянув лікар щелепу.

These alternatives change the emphasis or information focus, not the basic meaning.

For a learner, it is best to treat subject + verb + object as the default safe pattern.

Because Ukrainian has no articles.

English uses a/an and the, but Ukrainian does not. Whether something is a doctor, the doctor, a jaw, or the jaw is understood from context.

So Лікар оглянув щелепу could correspond to English in different ways depending on the situation, such as:

• doctor examined the jaw
• the doctor examined the jaw
• a doctor examined the jaw

English requires an article; Ukrainian usually does not.

They are:

• лікар = doctor
• оглянути = to examine, inspect
• щелепа = jaw

In the sentence:

• лікар stays in its dictionary form because it is nominative singular
• оглянув is a conjugated past-tense form of оглянути
• щелепу is the accusative singular form of щелепа

Learning to recognize the dictionary form behind the sentence form is a key skill in Ukrainian.

The letter щ is one of the sounds English speakers often notice right away.

In standard Ukrainian, щ is commonly pronounced something like a soft/sharp shch, and in many modern pronunciations it can sound close to a long soft sh. In щелепу, the beginning is roughly like shche-.

So щелепу starts approximately like:

• shche-

Just do not pronounce it like English ch alone.

No. That would be ungrammatical in standard Ukrainian.

After a transitive verb like оглянув, the direct object should be in the accusative case. So you need:

• щелепу, not щелепа

A good rule for beginners is:

• feminine nouns in -а often change to -у in the accusative singular when they are direct objects

In normal usage, щелепа usually means jaw and can refer naturally to the jaw area in a medical or anatomical sense. Like many body-part words, the exact scope depends on context.

So in a sentence like this, it is a natural choice for saying that a doctor examined someone's jaw.